On 2006-07-13 at 02:29BST "Neil Mitchell" wrote:

Hi,

...

Are cool kids supposed to put the comma in front like this? Some cool kids do, some cool kids don't. Some do both, depending on their mood.

The advantage of a leading , is that now the comma's line up, and if you want to add an item on the end of a list

[a ,b ,c ]

It's just a one line change, whereas with the comma after, you'd have to change the previous line as well - which is more effort and gives more noise in the darcs copy.

This is one of my pet hates. First, people find things easier to read if they are in a form that they have encountered lots of times before (in addition to psycho-visual factors). I'd like to think that Haskell programmers read a lot of literature (and since they should have started reading this long before they learnt to programme, and continue so to read, they're going to have read more literature than code). So for me (and anyone else moderately literate) a list written [a, b, c ] is easier to read and, (for folk who read from left to right) gives emphasis to the important parts rather than the punctuation. (Of course, a list with elements that short would just be written [a, b, c] anyway.) Now, you argue that it's more effort to add (or delete) items from lists in this form, and maybe you are right (I do it by dragging my mouse over stuff I want to remove, so start with the comma and go down; it doesn't seem too hard. If you want keystroke commands, you want something that respects the syntax). The thing is, making modifications that change the meaning /ought/ to be effortful. If you can delete things without thinking about it, you're probably going to delete something you shouldn't. Then the argument from darcs -- well, historically diff is line based, which was fine in the days of punch-cards, but makes much less sense nowadays. Ideally the diff darcs uses should be syntax driven -- a nice project for someone; we can save effort by only doing this for Haskell, and leave programmers in other languages stuck with line-by-line diffs. Jón -- Jón Fairbairn Jon.Fairbairn at cl.cam.ac.uk

On 2006-07-13 at 11:15+0200 Henning Thielemann wrote:

Optimal notation of lists, because of most easiest editing, is

a: b: c: []

That made me smile. In Ponder I had used up : for types, and lists could be a:: b:: c:. but when I suggested this at a Haskell meeting, Simon PJ complained that it "looks like hopscotch". I've never quite understood that complaint! Jón -- Jón Fairbairn Jon.Fairbairn at cl.cam.ac.uk

On 2006-07-13 at 09:35EDT mark@ixod.org (Mark T.B. Carroll) wrote:

Jon Fairbairn writes:

...

a:: b:: c:.

but when I suggested this at a Haskell meeting, Simon PJ complained that it "looks like hopscotch". I've never quite understood that complaint!

http://blogs.salon.com/0002296/myimages/hopscotch.jpg and http://www.northshield.org/officers/seneschal/moy/games/hopscotch.gif suggest to me that the pattern of : and . going up in a row is a bit like the squares along the linear 'course' (or list (-:) where sometimes you get one and sometimes two.

Well, perhaps (the pattern I associate with hopscotch is the first, ie ·:·:·:·, which could never happen since :. is the end of the list), but that still leaves open the question "What's bad about that?" :-) Jón -- Jón Fairbairn Jon.Fairbairn at cl.cam.ac.uk